Large area light sources have many applications including, for example, backlighting liquid crystal displays (LCDs) for watches, clocks, pagers, hand-held computers, organizers and the like. Such large area light sources typically employ a thin, flat lighting panel illuminated by one or more miniature lamps, light emitting diodes or the like positioned along at least one of the edges of the lighting panel. The light radiated by the lamps enters the edges of the lighting panel and is reflected through the panel and emitted from one of the planar surfaces of the panel for illuminating the LCD.
It is generally desirable to provide the LCD with a uniform distribution of light so that the entire surface of the LCD may be easily read in most ambient light conditions. Many available lighting panels are configured to maximize the uniform distribution of light emitted from the lighting panel. However, one limitation in achieving a uniform light distribution is that the light radiated by the light source (lamp) is not uniformly distributed along the edge of the lighting panel even when a reflector or the like is used to improve the light coupling efficiency of the lamp. The light radiated by the lamp typically has a bright spot or area of high light concentration. If several lamps are required, the lamps are separated by areas of shadow or low light intensity which may produce longitudinal-striations in the output of the lighting panel. Using several lamps to illuminate the lighting panel also increases the cost of the large area light source. Providing uniform lighting along the edge of the lighting panel would increase the uniform distribution of light emitted by the lighting panel.